1. Field of the invention
The present invention relates to a hydraulic sealed-type automatic tensioner for tensioning belts, chains and the like.
2. Description of the Prior Art
There are known various hydraulic automatic tensioners for tensioning belts, chains and the like, the tensioners being analogous in structure to hydraulic lifters used in the valve trains of internal combustion engines. One conventional design of such hydraulic lifter or hydraulic automatic tensioner is of the open type used with an oil pan as disclosed in U.S. Pat. No. 3,875,908. Another prior hydraulic lifter has a sealed construction as shown in U.S. Pat. No. 2,815,740. The open-type automatic tensioner can only be used in limited locations as it requires to be combined with the oil pan. The hydraulic automatic tensioner of the sealed design utilizes axial movement of a plunger in a body, and also finds only limited use since the plunger has a large diameter and a small stroke.